visual pathways
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Inconsistent information from different modalities can be delusive for perception. This phenomenon can be observed with simultaneously presented inconsistent numbers of brief flashes and short tones. The conflict of bimodal information is reflected in double flash or fission, and flash fusion illusions, respectively. The temporal resolution of the vision system plays a fundamental role in the development of these illusions. As the parallel, dorsal and ventral pathways have different temporal resolution we presume that these pathways play different roles in the illusions. We used pathway-optimized stimuli to induce the illusions on separately driven visual streams. Our results show that both pathways support the double flash illusion, while the presence of the fusion illusion depends on the activated pathway. The dorsal pathway, which has better temporal resolution, does not support fusion, while the ventral pathway which has worse temporal resolution shows fusion strongly.
- MeSH
- akustická stimulace MeSH
- časové faktory MeSH
- iluze * MeSH
- lidé MeSH
- mladý dospělý MeSH
- psychometrie MeSH
- sluchová percepce MeSH
- světelná stimulace metody MeSH
- teorie detekce signálu MeSH
- zraková percepce * MeSH
- zrakové dráhy fyziologie MeSH
- zrakové korové centrum fyziologie MeSH
- Check Tag
- lidé MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Audio-visual integration has been shown to be present in a wide range of different conditions, some of which are processed through the dorsal, and others through the ventral visual pathway. Whereas neuroimaging studies have revealed integration-related activity in the brain, there has been no imaging study of the possible role of segregated visual streams in audio-visual integration. We set out to determine how the different visual pathways participate in this communication. We investigated how audio-visual integration can be supported through the dorsal and ventral visual pathways during the double flash illusion. Low-contrast and chromatic isoluminant stimuli were used to drive preferably the dorsal and ventral pathways, respectively. In order to identify the anatomical substrates of the audio-visual interaction in the two conditions, the psychophysical results were correlated with the white matter integrity as measured by diffusion tensor imaging.The psychophysiological data revealed a robust double flash illusion in both conditions. A correlation between the psychophysical results and local fractional anisotropy was found in the occipito-parietal white matter in the low-contrast condition, while a similar correlation was found in the infero-temporal white matter in the chromatic isoluminant condition. Our results indicate that both of the parallel visual pathways may play a role in the audio-visual interaction.
- MeSH
- akustická stimulace MeSH
- anizotropie MeSH
- bílá hmota fyziologie MeSH
- dospělí MeSH
- lidé MeSH
- mapování mozku MeSH
- sluchová percepce fyziologie MeSH
- světelná stimulace MeSH
- teorie detekce signálu fyziologie MeSH
- zobrazování difuzních tenzorů MeSH
- zobrazování trojrozměrné MeSH
- zraková percepce fyziologie MeSH
- zrakové dráhy fyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- hodnotící studie jako téma MeSH
- lidé MeSH
- testy zrakového pole metody využití MeSH
- zraková pole genetika MeSH
- zrakové dráhy patologie MeSH
- zrakové evokované potenciály fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- recenze MeSH
1st ed. 277 s.
UNLABELLED: Single cases may lead to unexpected hypotheses in psychology. We retrospectively analyzed single case studies that suggested organizational principles along the early visual pathway, which have remained unanswered until now. FIRST CASE: In spite of the inhomogeneity of sensitivity, paradoxically the visual field on the subjective level appears to be homogeneous; constancy of brightness of supra-threshold stimuli throughout the visual field is claimed to be responsible for homogeneity; specific summation properties of retinal ganglion cells are hypothesized to guarantee this effect. SECOND CASE: With a brain-injured patient having suffered a partial visual field loss it can be shown that color induction is a retinal phenomenon; lateral inhibitory processes at the level of amacrine cells are hypothesized as neural network. Third case: In a patient having suffered a bilateral occipital lobe infarction, some functional recovery has been demonstrated; divergence and convergence of projection in the ascending neural pathway are suggested as a structural basis for recovery. Slowed down binocular rivalry discloses a sequential mechanism in the construction of a visual percept. Fourth case: The pre-wired projection of the retina to the visual cortex in spite of a severe squint of one eye is confirmed, but paradoxically some local neuroplasticity is also suggested. Fifth case: Using habituation of local sensitivity in the visual field and its resetting by interhemispheric interactions as an experimental paradigm, it is suggested that spatial attention is controlled at the midbrain level. Sixth case: Observations on residual vision or "blindsight" support the hypothesis that the visual cortex is the one and only structure responsible for visual perception on a conscious level. The unifying principle of these retrospective analyses is that subjective visual phenomena can lead to unexpected but testable hypotheses of neural processing on the structural and functional level in the early visual pathway.
- MeSH
- lidé MeSH
- metathalamus fyziologie MeSH
- mozkový infarkt patofyziologie MeSH
- poranění mozku patofyziologie MeSH
- pozornost fyziologie MeSH
- retina fyziologie MeSH
- retrospektivní studie MeSH
- slepota patofyziologie MeSH
- světelná stimulace MeSH
- vnímání barev MeSH
- zraková pole * MeSH
- zrakové dráhy fyziologie MeSH
- zrakové korové centrum fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- kazuistiky MeSH
Classically, the pupillary pathway is considered as a simple reflex arc comprising retinal ganglion cells, midbrain interneurons, oculomotor nerve and short ciliary nerves. However, there are some specialties in the construction of the pupillary pathways that have to be kept in mind when dealing with diseases involving pupillary disorders. This may help to localise lesions. Additionally, studies in patients with lesions of the retrogeniculate pathways have shown that pupillary disorders are possible even with lesions not involving the classical reflex arc. The pupil is therefore not only controlled subcortically, some components are influenced by the visual cortex. The aim of this article is to clarify various findings and terms such as relative afferent pupillary defect and pupillary hemihypokinesia.
- MeSH
- aferentní nervové dráhy patofyziologie MeSH
- chiasma opticum patofyziologie MeSH
- interneurony fyziologie MeSH
- lidé MeSH
- mezencefalon patofyziologie MeSH
- nervus oculomotorius patofyziologie MeSH
- nervus opticus patofyziologie MeSH
- poruchy zornice etiologie patofyziologie MeSH
- reflex pupilární fyziologie MeSH
- retinální gangliové buňky fyziologie MeSH
- testy zrakového pole MeSH
- zrakové dráhy patofyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
